1. Field of the Invention
The present invention pertains to the field of metallic material, and belongs to the category of oxide dispersion strengthened materials. Particularly, there is provided a process in which powders of mixed oxides of yttrium oxide and ferric oxide are industrially fabricated at low cost and on a large scale by utilizing the recovery procedure of pickling liquors of industrial hydrochloric acid, and then are subjected to reduction and a densification process to fabricate an iron-based dispersion strengthened material.
Due to its low cost and good performance, the oxide dispersion strengthened iron-based material according to the present invention can be used on the occasions when excellent high-temperature strength and creep strength are required, such as material for the first wall of a nuclear fusion reactor, etc., and can be used to fabricate powder metallurgy parts of low cost and high performance besides.
2. Description of the Related Art
With the rapid development of science and technology, various thermal mechanics (gas turbines, jet engines, rockets), the aerospace industry, and the atomic energy industry have increasingly high requirements on high-temperature strength and corrosion-resistant property of heat-resistant materials. Currently, as regards a conventional heat-resistant metallic material, solid solution strengthening and precipitation hardening of precipitated phases are usually adopted as its main strengthening means. However, the precipitated phases will be aggregated and grow up at a high temperature or be solid-solved in the matrix again, so that the strengthening function is lost and its usage temperature is limited; and on the other hand, elements for solid solution strengthening each enormously reduce the anti-oxidation corrosion resistance. While for an iron-based oxide dispersion strengthened material, a metal is strengthened by a stable dispersed phase of an oxide, and accordingly, it is possible that the above limitations are overcome, the high-temperature properties and mechanical properties of general metals are improved, and the thermal stability, hardness and strength of high-temperature alloys are enhanced more effectively.
Dispersion strengthening is such a method: in a metal, second phase particles that are usually relatively stable are added or formed, so as to strengthen the alloy. The second phase particles are added into the matrix material artificially, and they are uniform, fine, and capable of pinning dislocations, particle boundaries, subparticle boundaries and impeding movement of dislocations, and have good thermal stability and chemical stability, to thereby strengthen the material. Moreover, they will not be dissolved any more when the alloy is heated to a higher temperature, and the strengthening effect can be maintained until it approximates the melting point of the alloy (0.8-0.9 Tmelting point), so that the dispersion strengthened material still has a quite high strength, creep property and anti-oxidation property at temperatures close to the melting point. As such, it is possible that potentials of the material are exploited to a great extent, and the metallic material is fully used. The second phase particles for bringing out the strengthening effect in the metallic material have to be fine particles that are dispersed in the metal by way of being relatively uniform. It is generally thought that the finer the oxide particles are, the more uniform the distribution is, and the improvement in properties of the material is more remarkable.
At present, for the preparation of iron-based oxide dispersion materials, what is mainly adopted is the mechanical alloying technology, in which they are fabricated through a mechanical alloying process, taking Fe as original powders, Cr, Al, Ti and Mo as intermediate alloy powders, and Y2O3 as second-phase particles for dispersion strengthening. This method suffers from the following drawbacks: it has a high cost and a long production cycle, is not easy to control, tends to introduce impurities to pollute the alloy, etc. It is difficult to achieve large-scale industrial production and to assure nonexistence of coarse dispersed-phase particles by this method. The high production cost limits the scope of use of iron-based dispersion strengthened materials, which are merely used in the high-end industry at present. Therefore, to develop a fabricating process of iron-based oxide dispersion strengthened bulk materials of low cost has an important meaning in reality and a great market potential.